1. © 2009 Prentice-Hall, Inc. 11

2. 2 Technology in Action Chapter 13 Behind the Scenes: The Internet: How It Works

3. © 2009 Prentice-Hall, Inc. 3 Chapter Topics Managing the InternetManaging the Internet Interaction between Internet componentsInteraction between Internet components Internet data transmission and protocolsInternet data transmission and protocols IP addresses and domain namesIP addresses and domain names FTP and TelnetFTP and Telnet HTML and XLMHTML and XLM How e-mail and instant messaging work and how to keep them secureHow e-mail and instant messaging work and how to keep them secure

4. © 2009 Prentice-Hall, Inc. 4 Management of the Internet Who owns the Internet?Who owns the Internet? –Individuals –Universities –Government agencies –Private companies Who manages the Internet?Who manages the Internet? –Nonprofit organizations –User groups Who pays for the Internet?Who pays for the Internet? –U.S. taxpayers –Businesses –Universities –Other countries

5. © 2009 Prentice-Hall, Inc. 5 Connecting Internet Service Providers Internet backboneInternet backbone –Collection of large national and international networks –Verizon, AT&T, Sprint Nextel, Qwest T lines – –High-speed fiber-optic communications lines designed to provide high throughput – –T-1 lines – –T-2 lines – –T-3 lines – –T-4 lines

6. © 2009 Prentice-Hall, Inc. 6 Network Access Points (NAPs) Points of connection between ISPsPoints of connection between ISPs –Once known as network access points (NAPs) Private sector companies make up the Internet systemPrivate sector companies make up the Internet system –Exchange data via Internet Exchange Points (IXPs) Switches send data on a specific route through the networkSwitches send data on a specific route through the network

7. © 2009 Prentice-Hall, Inc. 7 Points of Presence (POP) Bank of modems where individual users connect to an ISPBank of modems where individual users connect to an ISP

8. © 2009 Prentice-Hall, Inc. 8 The Network Model of the Internet Internet communications follows the client/server network modelInternet communications follows the client/server network model Clients request servicesClients request services Servers respond to requestsServers respond to requests

9. © 2009 Prentice-Hall, Inc. 9 The Network Model of the Internet Types of serversTypes of servers –Web servers Host Web pagesHost Web pages –Commerce servers Enable the purchase of goods and services over the InternetEnable the purchase of goods and services over the Internet –File servers Provide remote storage space for files that users can downloadProvide remote storage space for files that users can download

10. © 2009 Prentice-Hall, Inc. 10 P2P File Sharing

11. © 2009 Prentice-Hall, Inc. 11 Data Transmission and Protocols Computer protocols are rules for electronic information exchangeComputer protocols are rules for electronic information exchange Open system protocolsOpen system protocols –Any computer can communicate with other computers using the same protocols

12. © 2009 Prentice-Hall, Inc. 12 Circuit Switching Dedicated connection between two pointsDedicated connection between two points Remains active until the transmission is terminatedRemains active until the transmission is terminated Used in telephone communicationsUsed in telephone communications Inefficient for computersInefficient for computers

13. © 2009 Prentice-Hall, Inc. 13 Packet Switching Data is broken into small units called packetsData is broken into small units called packets Packets are sent over various routes to their destinationPackets are sent over various routes to their destination Packets are reassembled by the receiving computerPackets are reassembled by the receiving computer Packets containPackets contain –Destination/source addresses –Reassembling instructions –Data

14. © 2009 Prentice-Hall, Inc. 14 Packet Switching

15. © 2009 Prentice-Hall, Inc. 15 TCP/IP Transmission Control Protocol (TCP)Transmission Control Protocol (TCP) –Prepares data for transmission –Provides error-checking –Enables resending lost data Internet Protocol (IP)Internet Protocol (IP) –Responsible for sending data from one computer to another

16. © 2009 Prentice-Hall, Inc. 16 IP Addresses Unique number that identifies devices connected to the InternetUnique number that identifies devices connected to the Internet Typical IP addressTypical IP address – 197.24.72.157 Static addressStatic address –Address never changes Dynamic addressDynamic address –Temporary address

17. © 2009 Prentice-Hall, Inc. 17 Having Enough IP Addresses IPv4 addressing scheme didn’t foresee explosive growthIPv4 addressing scheme didn’t foresee explosive growth CIDR (Classless Inter-Domain Routing)CIDR (Classless Inter-Domain Routing) –Allows a single IP address to represent several unique addresses –Uses a network prefix (slash and number) –Identifies how many bits in the IP address are unique identifiers

18. © 2009 Prentice-Hall, Inc. 18 Having Enough IP Addresses Internet Protocol version 6 (IPv6)Internet Protocol version 6 (IPv6) –Longer IP addresses –Easier for non-PC devices to connect to the Internet

19. © 2009 Prentice-Hall, Inc. 19 Domain Names Name that takes the place of an IP addressName that takes the place of an IP address Sample domain nameSample domain name – www.mywebsite.com www.mywebsite.com Top-level domains (TLD)Top-level domains (TLD) –Portion of the domain name that follows the dot –Sample top-level domain names.com,.org,.edu, and.net.com,.org,.edu, and.net Second-level domainsSecond-level domains –Unique name within a top-level domain –Sample second-level domain names Yahoo.com, Google.com, and Unesco.org Yahoo.com, Google.com, and Unesco.org

20. © 2009 Prentice-Hall, Inc. 20 Domain Name Servers Internet servers that translate domain names to IP addressesInternet servers that translate domain names to IP addresses ISPs go first to a default DNS to resolve a nameISPs go first to a default DNS to resolve a name Name queries work up the hierarchy to the root DNS servers if requiredName queries work up the hierarchy to the root DNS servers if required

21. © 2009 Prentice-Hall, Inc. 21 Other Protocols File Transfer Protocol (FTP)File Transfer Protocol (FTP) –File-sharing protocol –Files are downloaded and uploaded using the Internet TelnetTelnet –Protocol for connecting to a remote computer and a TCP/IP service –Enables a client computer to control a server computer

22. © 2009 Prentice-Hall, Inc. 22 HTTP and SSL Hypertext Transfer ProtocolHypertext Transfer Protocol –Protocol for transferring hypertext documents –Hypertext documents are linked to other documents (through hyperlinks) Secure HyperText Transfer Protocol (S-HTTP)Secure HyperText Transfer Protocol (S-HTTP) Secure Socket LayerSecure Socket Layer –Security protocols that protect sensitive information –Encrypts data

23. © 2009 Prentice-Hall, Inc. 23 HTML/XHTML Hypertext Markup Language (HTML)Hypertext Markup Language (HTML) –Format for creating Web pages Extensible Hypertext Markup Language (XHTML)Extensible Hypertext Markup Language (XHTML) –Successor to HTML –Has much more stringent rules regarding tagging HTML/XHTMLHTML/XHTML –Not programming languages but sets of rules for marking up blocks of text so that a browser knows how to display them

24. © 2009 Prentice-Hall, Inc. 24 HTML/XHTML Example This is the Heading This is text using Arial font. This text is italicized. This text is bold. This text color is red. This is a hyperlink www.prenhall.com HTML/XHTML Web Page Display

25. © 2009 Prentice-Hall, Inc. 25 Extensible Markup Language (XML) Designed for information exchangeDesigned for information exchange Tools used to create your own markup languageTools used to create your own markup language Used in e-commerce transactionsUsed in e-commerce transactions

26. © 2009 Prentice-Hall, Inc. 26 Common Gateway Interface (CGI) Browsers request that a program file executes (runs)Browsers request that a program file executes (runs) CGI files often called CGI scriptsCGI files often called CGI scripts Adds Web page interactionAdds Web page interaction –Adding names to guest books/mailing lists –Completing forms

27. © 2009 Prentice-Hall, Inc. 27 Client-Side Applications A program that runs on a client computer with no interaction with the serverA program that runs on a client computer with no interaction with the server Types of client-side applications includeTypes of client-side applications include –HTML/XHTML document embedded with JavaScript code –Applet: Small program that resides on the server

28. © 2009 Prentice-Hall, Inc. 28 Communications Over the Internet E-mailE-mail –Simple Mail Transfer Protocol (SMTP) –Multipurpose Internet Mail Extensions (MIME)

29. © 2009 Prentice-Hall, Inc. 29 Communications Over the Internet E-mail securityE-mail security –Encryption Private-key encryptionPrivate-key encryption Public-key encryptionPublic-key encryption –Secure data transmission software SafeMessageSafeMessage

30. © 2009 Prentice-Hall, Inc. 30 Instant Messaging (IM) Client/server program for real-time, text- based conversationsClient/server program for real-time, text- based conversations Popular IM programsPopular IM programs –AOL Instant Messenger –ICQ –Yahoo! Messenger –MSN Messenger Increasing security threatsIncreasing security threats –Should not be used for sensitive data

31. © 2009 Prentice-Hall, Inc. 31 Chapter 13 Summary Questions Who manages and pays for the Internet?Who manages and pays for the Internet?

32. © 2009 Prentice-Hall, Inc. 32 Chapter 13 Summary Questions How do the Internet’s networking components interact?How do the Internet’s networking components interact?

33. © 2009 Prentice-Hall, Inc. 33 Chapter 13 Summary Questions What data transmissions and protocols does the Internet use?What data transmissions and protocols does the Internet use?

34. © 2009 Prentice-Hall, Inc. 34 Chapter 13 Summary Questions Why are IP addresses and domain names important for Internet communications?Why are IP addresses and domain names important for Internet communications?

35. © 2009 Prentice-Hall, Inc. 35 Chapter 13 Summary Questions What are FTP and Telnet, and how do I use them?What are FTP and Telnet, and how do I use them?

36. © 2009 Prentice-Hall, Inc. 36 Chapter 13 Summary Questions What are HTML and XML used for?What are HTML and XML used for?

37. © 2009 Prentice-Hall, Inc. 37 Chapter 13 Summary Questions How do e-mail and instant messaging work, and how are messages kept secure?How do e-mail and instant messaging work, and how are messages kept secure?